A press for producing such products and especially a multilevel press generally comprises a press stand with a single press frame or a plurality of press frames arrayed in a row and wherein each press frame is comprised of a frame head piece and a frame foot piece as well as a pair of lateral shanks under tension connected between the frame head piece and the frame foot piece.
The tensionable shanks can be formed at their ends with hammerheads or formations equivalent to hammerheads which overlie or underlie horizontal bearing surfaces on the frame head piece or the frame foot piece.
In a multilever press of that type, a stationary press head is supported by the head pieces of the frames and is juxtaposed with a movable press bed on the foot pieces of the frames, the press bed being displaceable upwardly and downwardly by, for example, piston-and-cylinder arrangements below the press bed and integrated into the foot pieces of the frame. Between the bed and the head, a plurality of press platens can be provided and between pairs of platens, the workpieces in the form of pressboard mats can be hot pressed to produce the pressed board. The press platens, the head and the bed can all be formed preferably as heated plates.
The multilevel press can be provided on each side with at least one simultaneous closure device which permits the platens to close relative to one another simultaneously as the bed is raised.
Multilevel presses of this type, using press frames arrayed in a row, have had the press stand and especially the press frames constructed completely from steel plates which can be welded, bolted or riveted together from steel plate sections or segments.
Press frames of this type can have horizontal joints between the shanks and the headpiece and/or foot piece and between segments of the uprights. In the region of the joints at which the shanks are to be connected to the head and foot pieces at least, thicker connecting pieces are required and are secured to the steel plates by rivets or bolts so that the frame structures can take up the press forces without deformation (see, for example, German Patent Document 195 00 983 C1).
Multiplaten presses having a frame construction wherein the frame is under tension at least during the pressing stage and having tension rods between force-receiving corner members of the frame head part and foot part have also been provided. To maximize the ability to absorb shear and bending sources, the two lateral tension members are constituted as double-T girders and/or box profiles in German Patent Document DE 44 08 101 and equivalent U.S. Pat. No. 5,611,271.
German Patent Document DE 102 41 119 A1 (U.S. Pat. No. 6,851,358) describes a multilevel press in which the frame shanks have hammerheads as previously described and the hammerheads themselves can bridge head pieces of the frames. The head pieces, foot pieces and other parts of the frame can be fabricated from steel plate sections.
Finally, mention should be made of a type of column press which has been used in the field and which connects the head and base of the press together by press columns which generally are cylindrical in shape. In such a column press with cylindrical columns, the head part and the foot part are composed of castings, with such presses, a problem arises in that with increasing width of the press the space at the sides becomes more limited since the diameters of the cylindrical press columns must increase as a function of the square of the press width. With increasing widths, the heating plates or platens must be of greater thickness to avoid sag. This means that any closing mechanism must be of greater dimensions than would otherwise be advantageous and that requires more space. Such presses, therefore, are unwieldly.